1. Technical Field
The invention relates to a shrinkage disc unit which can in particular serve to connect two shafts. It further relates to a tool for establishing and/or releasing an interference fit assembly formed by the shrinkage disc unit. Lastly, it relates to an assembling and/or disassembling array, i.e. a combination of the shrinkage disc unit and the tool, for establishing and/or releasing the interference fit assembly.
2. Description of the Related Art
In many applications, two shaft ends are connected, for transferring torque, by a cylindrical interference fit assembly, wherein one shaft end is embodied as a hollow cylindrical shaft, into which the other shaft end, which is generally formed as a solid cylindrical shaft, is inserted. An additional sub-assembly is placed on the cylindrical outer surface of the hollow shaft and exerts a force directed radially inwards on the hollow shaft. This force causes the cylindrical inner surface of the hollow shaft to be pressed onto the cylindrical outer surface of the solid shaft, generating a frictional lock which can transfer torques and axial forces from one shaft end to the other.
Such a shrinkage assembly is for example used in wind power plants, to connect the rotor shaft to the input shaft of the gear system. Such an assembly is also a preferred example application of the invention.
A so-called shrinkage disc is then preferably used as the sub-assembly for generating the radial pressing, wherein a thick-walled, internally conical hub is mechanically or hydraulically pushed onto a thin-walled, externally conical tensioning sleeve. A cylindrical inner surface of the tensioning sleeve sits on the cylindrical outer surface of the hollow shaft. Pushing the hub onto the tensioning sleeve exerts the radially acting force described on the hollow shaft.
The two currently most common shrinkage disc designs comprise integrated devices which make external tools for assembling and disassembling substantially superfluous. Only spanners or hydraulic pumps are needed as external tools for assembling and disassembling the shrinkage discs. The axial force for pushing the hub onto the tensioning sleeve is generated either by tensioning screws or by a hydraulic chamber.
For disassembling one design, the tensioning screws are released. The conical surface assembly between the tensioning sleeve and the hub is embodied to not be self-locking, such that the hub slips from the tensioning sleeve by itself. In the other design, a second hydraulic chamber is installed which, for disassembling, generates an axial force, pointing towards the small diameter of the cone, onto the hub. The tensioning sleeve thus pushes the hub, against the self-locking in the conical joint between the hub and the tensioning sleeve.
Integrating the devices for generating the axial force for assembling and disassembling is very complicated and therefore leads to significantly higher production costs. Given that for a plant life of for example 20 years, the assembling and disassembling process shall only be performed once or twice, the complexity of integrating these devices is economically inappropriate.
Assembling a shrinkage disc of the first design on the hollow shaft is very time-consuming, since the tensioning screws distributed in large numbers on the circumference have to be screwed tight in stages, up to the maximum assembling torque, in order to prevent the shrinkage disc from being unevenly tensioned. In addition, intervals must be inserted which are necessitated by fitting processes of the screw connections and the necessary re-tensioning. Assembling the shrinkage disc is therefore considerably time-consuming.
A shrinkage disc of the second design has a significantly larger constructional length than the cone needed for generating the radial pressing, due to the integration of the hydraulic chamber for generating the assembling force. The larger constructional length also necessitates a longer hollow shaft, in order to provide the installation space for the shrinkage disc. The mass and the moment of inertia of the plant increase, which in many applications can result in a negative effect on operations.